Seeding machines typically are provided with a transversely extending main frame having transversely extending left and right wing frames. The main frame is provided with a forwardly extending drawbar for attachment to a tractor. Planting units may be transversely distributed along the main frame and the left and right wing frames. The wing frames are normally folded to reduce the transverse width of the seeding machine during transport. In some seeding machine configurations the wing frames are forwardly folded substantially parallel to the drawbar for reducing the transverse width. The individual planting units are typically provided with seed hoppers for holding the seed to be planted. The seed is typically loaded into the planting unit seed hoppers one at a time by the operator. Some seeding machines having planting units are provided with pneumatic seed on demand delivery systems in which the planting unit seed hoppers are automatically refilled with seed as needed from a main hopper.
Pneumatic seed on demand delivery systems automatically direct seed from a main seed hopper to a plurality individual planting units. Each of the individual planting units has an auxiliary seed hopper for receiving the seed, a seed meter for metering the seed from the auxiliary seed hopper and a furrow opener for forming a planting furrow into which the metered seed is deposited. A fan is used to create pressurized air that forms an air stream on which the seed is taken to the planting units. These systems automatically replenish the auxiliary hoppers as needed.
Pneumatic seed on demand seeding machines typically have a large central seed hopper that supplies seed to all of the auxiliary hoppers on the planting units. The main seed hopper and pneumatic seed on demand distribution system may be located on a trailing cart or on the main frame itself.